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The preoperative assessment of obstetric patients

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The importance of early identification and management of the high-risk obstetric patient is emphasised in the Confidential Enquiry into Maternal and Child Health (CEMACH) report. High-risk patients who need anaesthetic input include those with airway problems, cardiorespiratory disease and rare genetic conditions, such as malignant hyperthermia and suxamethonium apnoea. Anaesthetic options for labour analgesia as well as anaesthesia for operative delivery will need to be discussed in detail with the patient if a delivery management plan is to be constructed. Input from other medical teams, such as cardiologists or haematologists, are often needed. Ultimately, these measures should reduce maternal morbidity and mortality.

Section snippets

The relevance of pre-assessment

Despite numerous advances in medicine, obstetrics and anaesthesia, maternal mortality rates have remained fairly constant in the United Kingdom (UK) and the United States (US) in the past few decades. One reason for this is the growing number of high-risk patients becoming pregnant, including those with advanced maternal age, obesity and significant cardiovascular, respiratory and neurological conditions. The management of high-risk pregnant patients is amongst some of the most challenging

Assessment and recognition of the difficult airway

For over 2 decades, despite various advances in the management of the pregnant patient, the incidence of failed intubation in the obstetric population remains around 1 in 300 cases, which is approximately 10 times higher than in the general population. At the same time airway complications remain the leading cause of anaesthetic death amongst parturients.1 Majority of cases of failed intubation have occurred in the context of an emergency CS under general anaesthesia (GA)3, 4, which is

Induction of anaesthesia

A period of pre-oxygenation using a tight-fitting mask connected via hollow tubing to an anaesthesia machine is performed immediately prior to the administration of intravenous drugs to induce anaesthesia. Following this, the anaesthetist will pass an endotracheal tube (ETT; intubate) through the vocal cords with the aid of a laryngoscope blade. If the anaesthetist has difficulty in intubating the patient, the initial safest option is to maintain oxygenation using facemask ventilation. Airway

Airway assessment

The majority (>90%) of airway disasters could potentially be predicted.17 This is possible by a thorough examination of patients' airways in a non-urgent setting, such as in the preassessment clinic. By performing a few simple tests (e.g., Mallampati test, thyromental distance, atlanto-axial extension and mandibular protrusion), we can recognise the signs of a potentially problematic airway. The patient can then be referred to an anaesthetist and an appropriate early management plan created.

Mallampati test (Fig. 1)

This test assesses the size of the tongue in relation to the oropharynx.18 It is performed with the patient sitting with their mouth wide open and tongue protruded without phonation. The structures visible should be recorded as follows:

  • Mallampati class 1 – Uvula, tonsillar pillars, soft and hard palate all visible

  • Mallampati class 2 – Soft palate, hard palate and only base of the uvula are seen

  • Mallampati class 3 – Soft and hard palate are visible

  • Mallampati class 4 – Hard palate is visible only

Thrombophilia

Pregnancy is associated with a physiological hypercoagulable state. Venous thrombo-embolism occurs in 0.1% of pregnancies but is the most common direct cause of maternal death.1 Untreated calf-vein thrombosis and pulmonary embolism in pregnancy is associated with 15% and 25% mortality, respectively. Some women have hereditary (e.g., activated protein C resistance, antithrombin III deficiency, protein C or protein S deficiency) or acquired thrombophilia (e.g., antiphospholipid syndrome) or a

Cardiovascular disease in the pregnant patient

The latest CEMACH report showed that cardiac disease is the most common direct cause for maternal death and the second most common after thrombo-embolism.1

The spectrum of cardiac disease amongst mothers in the UK is very wide. However, there are some general principles applicable to each heterogeneous group, many of which have been outlined in the latest CEMACH report. The summary of those findings is outlined below:

  • 1.

    There is a distinct need to appreciate the profound impact of physiological

Respiratory disease and the pregnant patient

An increasing number of women with respiratory disease are becoming pregnant and, therefore, a variety of conditions, including obstructive and restrictive lung disease are encountered in the pre-assessment clinic. Pregnancy in itself profoundly affects respiratory function by causing tachypnoea, upward displacement of the diaphragm, decreased FRC and decreased forced expiratory volume (FEV1)/forced vital capacity (FVC) ratio <0.75. Frequently, all of the above changes are complicated further

Obesity and pregnancy

Obesity is a complex disorder, which presents a major challenge to every physician. In pregnancy, it is associated with increased morbidity and mortality due to hypertension, coronary artery disease, diabetes, cerebrovascular disease, fetal abnormalities and airway, obstetric and surgical complications.*48, 49 It affects over half of the US population (66% of North Americans are overweight with BMI of 25–29 and 32% are obese with BMI >29).50 A morbidly obese patient is one with a BMI >35. The

Backache

Chronic backache is the most common reason to take time off in the UK and is particularly common in pregnancy (up to 51% of pregnant women have experienced it at one point or another). About a third of women develop long-term chronic backache following childbirth. It is almost certain that anyone pre-assessing pregnant women would be faced with the problem of backache and, in particular, its association with epidurals. There is a widespread misconception amongst patients, midwives and some

Neurological disease and pregnancy

There are a variety of neurological conditions which can be encountered when pre-assessing pregnant women. Their management during pregnancy and the peripartum period should be by a multidisciplinary team involving a neurologist and an early referral to an anaesthetist in order to devise an optimal management plan with regard to medication, birth plan and discussing analgesic/anaesthetic options. Early antepartum consultation allows accurate documentation of any pre-existing neurological

Rheumatoid arthritis

Rheumatoid arthritis is a systemic autoimmune disease that is seen in about 0.1% of pregnancies. It runs a course of remissions and relapses and frequently improves with pregnancy.71 Rheumatoid arthritis affects mainly the small joints but the spine can also be involved, particularly the cervical spine. This makes patients with rheumatoid arthritis cases of difficult intubation if the temporo-mandibular and the crico-arytenoid joints are involved. A cervical flexion/extension X-ray is usually

Kyphoscoliosis

Kyphoscoliosis, curvature of the spinal column, may be congenital, associated with neuromuscular diseases such as muscular dystrophies, neurofibromatosis or cerebral palsy. In the pre-assessment clinic, we are more likely to encounter idiopathic kyphoscoliosis, which is more common in women and accounts for >80% of cases.72 Most women who present with this condition will have a mild deformity and some will have undergone corrective orthopaedic surgery. Severe forms of the disease will

Rare pharmacogenetic conditions relevant to obstetric anaesthesia

The pre-assessment clinic may be the first point of encounter for the obstetrician in a pregnant woman with malignant hyperpyrexia or suxamethonium apnoea.

These conditions are unrelated and have a completely different aetiology and pathophysiology. However, the one thing in common is their ability to cause serious and potentially lethal complications to susceptible individuals under GA.

Malignant hyperpyrexia (MH) is a rare familial condition in which a multi-system, catabolic and hyperthermic

Allergies and the obstetric patient

Allergies or ‘suspected allergies’ seem to be extremely common and the pre-assessment clinic is the place to ascertain the nature, severity and the exact triggering factor (s) of a particular allergic condition. In medical practice, patients frequently report they are allergic to antibiotics and must be questioned further about the exact nature of the reaction, that is, what exactly happened when they were given the drug, did they need to go to hospital, develop a rash, develop difficulty

HIV and the obstetric patient

Currently, there are an estimated 39 million people living with HIV worldwide of which 17 million are women, mostly of reproductive age. Due to improved therapeutic regimes (highly active antiretroviral therapy (HAART)), life expectancy has increased for people with HIV while at the same time the number of newly infected cases is on the rise. Therefore, obstetricians, anaesthetists and all those involved with women's health are almost certainly going to encounter HIV-positive parturients.

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